During an enucleation operation the entire eyeball is extracted from the orbital cavity. In evisceration, only the contents of the eyeball is extracted, the scleral shell remaining in place.
In both cases, in order to avoid leaving an empty orbital cavity, it has been known for along time to insert a synthetic prosthesis of spherical shape corresponding to the shape of the normal eye, either directly into the orbital cavity after enucleation or into the scleral shell after evisceration.
On the front of this synthetic prosthesis there is placed that which is commonly called a "glass eye", which in fact, is constituted by a plastic half-shell on which an iris and a pupil are marked, with the shell serving an esthetic purpose only.
The problem posed by such prior prostheses stems from being made of a material that is biocompatible but not colonizable, such as plastic (PMMA) or silicone, thus not enabling the prosthesis to be connected to the half-shell.
It is also known to make an intra-orbital implant comprising a silicone core covered in a biocolonizable material such as expanded PTFE. The drawback of such a prosthesis is that colonization can take place only at the periphery where the biocolonizable material is to be found thus likewise making it impossible to establish a connection between such an implant and the plastic shell.
In patent U.S. Pat. No. 4 976 731 (Perry), it is proposed to make the ball out of sterile porous hydroxyapatite ceramic obtained either from coral or by synthesis. The porosity of the hydroxyapatite prosthesis enables the implant to be colonized in its entirety. That colonization makes it possible subsequently to drill a hole into the ball enabling a driver to be inserted connecting the ball to the plastic half-shell. The driver provides better transmission of movements from the ball to the plastic shell, thereby enabling the artificial eye to move in a manner equivalent to the other eye.
Nevertheless, fabricating such an implant presents great difficulty of implementation associated with very high production costs.
That is in addition to the solubility of hydroxyapatite in the organism, which solubility is of the order of 3%, and gives rise to inflammatory reactions.